It creates a real problem in the wording rather than an automatic bar. The route is a nonimmigrant one for temporary entry, so a letter describing an indefinite, permanent appointment describes something the category does not contemplate. The right response is to have the employer state the actual period of the engagement.
Fix the description before it becomes evidence
Human resources departments write permanent because it distinguishes a staff position from a casual one, not because they have thought about immigration categories at all. Explain that plainly and ask for the letter to state the period the employer is engaging you for, along with the duties and the profession. Most employers will do it without difficulty once they understand why it matters, and the conversation also reveals whether the company has done this before. If the employer insists on describing an indefinite appointment, that is worth taking to counsel, because it may indicate the role is genuinely a permanent relocation and that a different route should be considered. Either way, the wording is far cheaper to address in draft than to explain later, when it has already been issued and relied on.
Hypothetical example: Emilio, a management consultant, receives an offer whose duties alternate between analysis and general account management. An opening assessment compares each duty with the listed professional role and asks the employer to identify which tasks are central. The offer letter, job description, organizational chart, and client statement are the records that settle the point. Sequence the work by agreeing on the professional category before requesting a revised letter. Trouble arises when a broad business title substitutes for a description of professional services, or when the individual would actually direct the enterprise receiving them. In that setting, clearer wording cannot cure a structure that amounts to self-employment; the arrangement itself has to be assessed.